Iwhat if this was after Sherlock died, and came back, so John wants Sherlock to be close to him, so they, like watch a movie (even though its obviously pointless to Sherlock to watch a movie because they're all predictable) and they fall asleep?

This is the part they didn’t show you in The Final Problem. That rope was for Sherlock to climb down into the well to John. John had been struggling to keep his head clear of the water for a good while, and he was getting exhausted